Recently, with rapid advancement of technology, electronic products such as portable loudspeakers, cell phones, mobile television sets, and voice navigation devices are equipped with a diversity of functions and made increasingly compact, thus allowing users to not only carry these electronic products around conveniently, but also enjoy their various functions anytime and anywhere.
Each of the above-cited electronic products is generally provided with at least one loudspeaker for reproducing music, voice, and/or other sounds, and it is well known that loudness of a loudspeaker depends, for an important part, on its physical size. However, as stated above, with compactness being the mainstream design concept for electronic products nowadays, loudspeakers used in such electronic products tend to be small and thus only produce low acoustic volume, particularly of the low-frequency range. In consequence, when electronic products of this kind are used to reproduce sound, it is unlikely for the user to hear the sound loud and clear, nor fully appreciate the low-frequency sound effect of the loudspeakers. Therefore, under the current trend in electronic product design, it is a pressing problem for loudspeaker manufacturers to balance between the dimension and the quality and volume of sound of a loudspeaker, with a view to offering optimal sound reproduction effect to consumers.
As a solution to the aforesaid problem, a sound reproduction device as shown in FIG. 1 was designed. Referring to FIG. 1, a sound reproduction device 1 includes a housing 10, a first loudspeaker 11, and a second loudspeaker 12. The housing 10 has an end formed with an opening. The housing 10 is also provided therein with an accommodating space. The first loudspeaker 11 includes a first frame body 110 having an end peripherally fixed to the housing 10 around a rim of the opening. Thus, the first frame body 110, along with a diaphragm, a coil, and a magnetic element provided in the first frame body 110, is received in the accommodating space. On the other hand, the second loudspeaker 12 includes a second frame body 120 having an end peripherally fixed to an inner periphery of the housing 10 between the first loudspeaker 11 and an opposite end of the housing 10. By means of the first loudspeaker 11 and the second loudspeaker 12, a closed resonance chamber 13 is defined in the accommodating space of the housing 10 as between the first loudspeaker 11 and the second loudspeaker 12, and a closed reflection chamber 14 is defined in the accommodating space of the housing 10 as between the second loudspeaker 12 and the opposite end of the housing 10.
The coil in each of the first and second loudspeakers 11, 12 is centrally provided at an inner periphery of the corresponding diaphragm. When a current flows through the coils in the first and second loudspeakers 11, 12, respectively, the coils are excited to generate field lines. Attraction and repulsion between the coils and field lines generated by the corresponding magnetic elements in the loudspeakers 11, 12 drive the diaphragms of the loudspeakers 11, 12 to vibrate synchronously. In consequence, air in the resonance chamber 13 and in front of the sound reproduction device 1 is vibrated to make sound. Now that the first loudspeaker 11 and the second loudspeaker 12 are connected by the closed resonance chamber 13, vibration of the diaphragms produces a compression effect as well as a vacuum effect on the air in the resonance chamber 13. In turn, the air in the resonance chamber 13 drives the diaphragms of the loudspeakers 11, 12 to vibrate even more vigorously, thereby increasing the loudness of sound reproduced. Meanwhile, air in the reflection chamber 14 is vibrated in the same direction and reflected by the opposite end of the housing 10 so as to cause secondary resonance. With the synchronous vibration and the secondary resonance in front of and behind the sound reproduction device 1, the sound reproduction device 1 produces a more significant low-frequency sound effect than a traditional loudspeaker.
However, the sound reproduction device 1 still has its shortcomings in use, as detailed below:
1. For the sound reproduction device 1 to reproduce sound, it is necessary that both the loudspeakers 11, 12 are driven. Therefore, the sound reproduction device 1, though capable of making sound at larger volume and producing more significant low-frequency sound effect than a traditional loudspeaker, consumes twice as much power, too. In other words, the sound reproduction device 1 works against the concept of energy saving and environmental protection that the entire world today endeavors to live up to.
2. While the sound reproduction device 1 is in operation, the loudspeakers 11, 12 must sound synchronously so as for the sound reproduction device 1 to make sound properly, without noise or audio signal interference. Hence, it is imperative that the specifications, circuits, and installation locations of the loudspeakers 11, 12 be strictly planned and designed; otherwise, the loudspeakers 11, 12 in the sound reproduction device 1 may not sound synchronously. Therefore, the sound reproduction device 1 incurs considerable costs of design and quality control during the design and production processes, which makes it impossible to effectively reduce the selling price of the sound reproduction device 1. And because of that, market competitiveness of the sound reproduction device 1 may be seriously impaired.
3. In addition, since the sound reproduction device 1 requires two loudspeakers, material costs of the sound reproduction device 1 are lofty. This also contributes to the high selling price and low market competitiveness of the sound reproduction device 1.
Hence, it is an important goal of the present invention to design a sound reproduction device which, under the premise of providing high sound volume and enhanced low-frequency sound effect, is capable of effectively lowering the costs of production, quality control, design, and materials, as well as working in accordance with the concept of energy saving and environmental protection, thereby solving the aforementioned problems of the traditional loudspeakers or sound reproduction devices.